The invention relates to a non return valve for an airbag of a vehicle passenger retention system, which forms a flow connection between two chambers of the airbag and at least partly prevents a flowing back of gas from the second chamber into the first chamber. The invention further relates to an airbag for a vehicle passenger retention system with a non return valve of this kind.
It is known to control, by means of a non return valve, the flow connection between the chambers in an airbag for a vehicle passenger retention system with the airbag having a plurality of chambers which are in flow connection with one another.
Thus WO 97/01461 describes an airbag with two chambers which are in flow connection with one another through a non return valve. The non return valve prevents a flowing back of gas from the second chamber back into the first chamber when the internal pressure in the first chamber is lower than the internal pressure acting in the second chamber. Otherwise it opens the flow connection between the two chambers.
The object of the invention is to provide a non return valve of the initially named kind for an airbag and, respectively, an airbag with a non return valve of this kind, through the use or which and in which, respectively, a flowing back of the gas from the second chamber into the first chamber is prevented even at high pressure differences between the chambers.
The invention satisfies this object through a non return valve having a connection hose between the first and the second chamber in which a fabric inlay is accommodated which subdivides the connection hose into a flow passage between the first and the second chamber and a pressure chamber which is in connection with the second chamber. The fabric inlay opens the flow passage when the internal pressure in the second chamber is lower compared to the internal pressure in the first chamber. When the internal pressure is higher in the second chamber the fabric inlay closes off the flow passage by means of the internal pressure which acts in the pressure chamber. Furthermore, the object is satisfied by an airbag having the features described further below.
In the invention, the connection hose, which forms the flow connection between the two chambers, is subdivided by the fabric inlay into the actual flow passage and the pressure chamber. Whereas the flow passage is connected to both chambers, the pressure chamber is in connection only with the second chamber. If now the internal pressure in the first chamber is greater than that in the second chamber, the gas flows through the open flow passage into the second chamber. With increasing internal pressure in the second chamber the internal pressure acting in the pressure chamber, which is bounded by the fabric inlay, also increases, through which the fabric inlay is prestressed against the pressure acting in the flow passage. As soon as the internal pressure in the second chamber exceeds the internal pressure in the first chamber, the internal pressure acting in the pressure chamber is so high that the fabric inlay is moved against the flow pressure in the flow passage and closes off the flow passage. The pressure force, with which the fabric inlay closes the flow passage, increases with increasing pressure difference between the two chambers, so that the non return valve remains closed even at high pressure difference.
Further advantageous developments of the invention result from the following description, the drawings and the subordinate claims.
Thus in a particularly preferred embodiment, the fabric inlay is folded back to form a funnel-shaped hose and is connected to the inner wall of the connection hose near the peripheral edge of its funnel opening of larger flow cross-section. The fabric inlay is only partly connected to the inner wall of the connection hose near the peripheral edge of its funnel opening of smaller flow cross-section which protrudes into the connection hose in the direction of the second chamber. Through the funnel-shaped folding back of the fabric inlay, the fabric inlay is elastically initially prestressed in the region of its funnel opening of smaller flow cross-section, so that as soon as the internal pressure in the second chamber drops below the internal pressure acting in the first chamber after the closing of the non return valve, the non return valve opens again easily.
In a further embodiment of the non return valve a further fabric inlay is provided which is connected to the first fabric inlay and forms together with the latter a hose with approximately the same cross-section. In this the hose is connected near its inlet opening facing the first chamber to the inner wall of the connection hose, whereas its part which protrudes in the direction of the second chamber into the connection hose is freely movably accommodated in the connection hose. Through the use of the second hose in the connection hose a circumferential pressure chamber is formed so that the two fabric inlays forming the hose are uniformly pressed together approximately over their entire length when the internal pressure acting in the second chamber is greater, through which a particularly high sealing action is achieved.
Particularly advantageous is also a third embodiment of the non return valve in accordance with the invention in which the fabric inlay is connected in such a manner near its one side edge facing the first chamber to a part of the inner wall of the connection hose that an inlet opening which is bounded by the fabric inlay and the inner wall of the connection hose is formed. The fabric inlay is passed diametrically through the connection hose and is connected near its other side edge facing the second chamber at the inner wall of the connection hose to form an outlet opening, with the flow cross-section of the outlet opening being smaller than that of the inlet opening. In this design of the non return valve as well a comparatively large pressure chamber is formed in which the internal pressure which is present in the second chamber acts uniformly on the fabric inlay and prestresses against the connection hose when the pressure difference between the two chambers is sufficiently large, so that the flow passage in the connection hose is closed.
The connection hose can likewise be formed of two fabric partial pieces, preferably of two fabric partial pieces of the airbag, and is sealed off at its edges, preferably through sewing. Through the use of a multiple part connection hose it is possible to sew together the fabric inlay for forming the funnel-shaped hose in accordance with the first exemplary embodiment, or for forming the hose in accordance with the second exemplary embodiment with the edges of the two fabric partial pieces, through which a particularly durable non return valve is formed.
The invention will be explained in the following in more detail with reference to three exemplary embodiments and with reference to the drawings. Shown therein are: